Can't hear sound

I'm sorta just fooling around with iMovie HD and I remember back with iMovie '04 I couldn't import mpeg movies I took from my digital camera. Now I could for some reason however there is no sound. I have a Sony digital camera and I've heard things about the format they use or something not allowing things to work right or something, I'm not sure.

It's not a big deal, just fooling around for now. But any ideas to why there is no sound with the video? However when I import some .mov files they work fine.

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